Operations with Decimals! Adding and Subtracting Decimals How is adding and subtracting decimals...
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Transcript of Operations with Decimals! Adding and Subtracting Decimals How is adding and subtracting decimals...
Operations with Decimals!
Adding and Subtracting DecimalsHow is adding and subtracting decimals similar to adding and subtracting whole
numbers?
Activities 1-3 – See handout
• Is there a relationship between adding and subtracting decimals and adding and subtracting whole numbers?
• When in the real world would you add and subtract decimals?
Steps for adding and subtracting
• Write the numbers down vertically.• Line up the decimal points. • Bring the decimal point straight down.• Add and subtract as you would whole
numbers.
Examples
• Add 8.13 and 2.76. 8.13 +2.76
• Add 1.459 + 23.7 1.459 + 23.7___
Examples
• Subtract 5.508 – 3.174.
5.508 - 3.174
• Subtract 21.9 – 1.605. 21.900 - 1.605
Real – Life Application
$3.45 $10.00+$3.90 - ______
Your turn
• Complete with your clock partner and then get your answers checked by me.
• 4.206 + 10.85 =
• 27.9 – 0.905 =
Conclusion
• How is adding and subtracting decimals similar to adding and subtracting whole numbers?
Multiplying Decimals
How is multiplying decimals similar to and different from multiplying whole
numbers?
Activity – Multiplying Decimals by Decimals
• Complete Activity (pages 7 and 8)• What conjecture can you make about the
relationships between multiplying decimals and multiplying whole numbers?
Steps to Multiplying Decimals
• Multiply as you would with whole numbers. • Count the number of decimal places in the
decimal factor. • The product has the same number of decimal
places.
Examples
• It is helpful to estimate to see if your answer is reasonable!
• Find 6 x 3.91
• Find 3 x 0.0016.
Examples
• Multiply 4.8 x 7.2.
• Multiply 3.1 x 0.05.
Real Life Application
• You buy 2.5 pounds of tomatoes. You hand the cashier a $10 bill. How much change should you receive?
Conclusion
• How is multiplying decimals similar to and different from multiplying whole numbers?
Dividing Decimals
How can you model decimal division with pattern blocks and numbers?
Complete Activity 1 on Division Modeling
• Dividing decimals by whole numbers– Place the decimal point in the quotient above the
decimal point in the dividend.– Then divide as you would with whole numbers.
– Find 7.6 ÷ 4 Find 36.4 ÷ 2
Dividing Decimals by Decimals
• Multiply the divisor and dividend by a power of ten to make the divisor a whole number.
• Place the decimal point in the quotient and divide as you would with whole numbers.
Examples
• Find 18.2 ÷ 1.4.
• Find 9.6 ÷ 1.2
• Find 0.459 ÷ 0.51
Real – World Example
Summary
• How can you model decimal division with pattern blocks and numbers?
• How else can you divide if you don’t draw or use a model?